/Engine/Source/Runtime/Engine/Public/MaterialHLSLTree.h
Mechanics of passing values from PS->VS are specific to material shaders, to VertexInterpolator is included in the Material module Possible that parts of this could be moved to the common HLSLTree module, if interpolators are needed by another system
class FExpressionVertexInterpolator : public [UE::HLSLTree::FExpression](API\Runtime\Engine\HLSLTree\FExpression)
constFExpressi...
VertexExpression